ASTM B930-03(2021)

Standard Test Method for Rating Grain Size and Frequency of Abnormally Large Grains in Cemented Tungsten Carbides (Hardmetals)

SIGNIFICANCE AND USE
5.1 The microstructure and grain growth of cemented tungsten carbides affect the material's mechanical and physical properties. The grain size and distribution will affect the material's wear resistance and fracture toughness. Abnormally large grains as compared to the background may introduce an area of weakness in a sintered part.  
5.2 This test method may be used in acceptance testing of cemented tungsten carbide materials or the tungsten carbide powder used in their manufacture. The specified grain size used for the E-Rating is to be agreed upon between purchaser and supplier.
SCOPE
1.1 This test method describes a procedure for measuring abnormally large grains and the frequency of those grains in cemented tungsten carbides (hardmetals).  
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Aug-2021
• ICS: 77.160 - Powder metallurgy
• Technical Committee: B09 - Metal Powders and Metal Powder Products
• Drafting Committee: B09.06 - Cemented Carbides

Relations

• Refers: ASTM B665-19 - Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides
• Effective Date: 01-Nov-2019
• Refers: ASTM B243-18 - Standard Terminology of Powder Metallurgy
• Effective Date: 01-Oct-2018
• Refers: ASTM B243-16 - Standard Terminology of Powder Metallurgy
• Effective Date: 01-Jul-2016
• Refers: ASTM B243-13 - Standard Terminology of Powder Metallurgy
• Effective Date: 01-Nov-2013
• Refers: ASTM B665-08(2012) - Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides
• Effective Date: 01-Oct-2012
• Refers: ASTM B243-12 - Standard Terminology of Powder Metallurgy
• Effective Date: 15-Jul-2012
• Refers: ASTM B243-11 - Standard Terminology of Powder Metallurgy
• Effective Date: 15-Nov-2011
• Refers: ASTM B657-11 - Guide for Metallographic Identification of Microstructure in Cemented Carbides
• Effective Date: 01-Oct-2011
• Refers: ASTM B406-96(2010) - Standard Test Method for Transverse Rupture Strength of Cemented Carbides
• Effective Date: 01-Sep-2010
• Refers: ASTM B243-10 - Standard Terminology of Powder Metallurgy
• Effective Date: 15-Jan-2010
• Refers: ASTM B243-09a - Standard Terminology of Powder Metallurgy
• Effective Date: 15-Dec-2009
• Refers: ASTM B243-09 - Standard Terminology of Powder Metallurgy
• Effective Date: 01-Jan-2009
• Refers: ASTM B665-08 - Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides
• Effective Date: 01-Nov-2008
• Refers: ASTM B243-08a - Standard Terminology of Powder Metallurgy
• Effective Date: 15-Mar-2008
• Refers: ASTM B243-08 - Standard Terminology of Powder Metallurgy
• Effective Date: 01-Feb-2008

Overview

ASTM B930-03(2021) - Standard Test Method for Rating Grain Size and Frequency of Abnormally Large Grains in Cemented Tungsten Carbides (Hardmetals) - provides a recognized and repeatable methodology for evaluating the microstructure of cemented tungsten carbides, particularly by measuring the occurrence and size of abnormally large grains. Developed by ASTM International, this standard plays a crucial role in ensuring the quality and consistency of hardmetals used in demanding applications where wear resistance and mechanical strength are critical.

Cemented tungsten carbides, also known as hardmetals, are widely used in cutting tools, mining equipment, and wear-resistant parts due to their exceptional hardness and toughness. The presence of abnormally large grains within the microstructure can significantly impact the mechanical and physical properties of the material, affecting its performance in industrial use.

Key Topics

• Microstructure Analysis: The standard outlines procedures for preparing, etching, and metallographically examining specimens of cemented tungsten carbides to identify grain structure characteristics.
• E-Rating and L-Rating: Defines two quantitative metrics:
  • E-Rating: The number of grains larger than a specified size per square centimeter in a fully etched specimen.
  • L-Rating: The size in micrometers of the largest grain observed.
• Quality Assurance: Offers methods for acceptance testing of cemented tungsten carbide materials, helping to ensure that products meet agreed-upon grain size specifications between purchasers and suppliers.
• Impact on Properties: Highlights the significance of grain size and distribution on wear resistance and fracture toughness; abnormally large grains may weaken sintered parts by forming potential failure sites.

Applications

The test method described in ASTM B930-03(2021) has broad application across industries utilizing cemented tungsten carbides:

• Manufacturing and Quality Control: Utilized during acceptance testing of cemented tungsten carbide blanks and finished parts to ensure material integrity and adherence to specifications.
• Materials Development: Supports R&D by providing a standardized approach to assess the effects of powder processing and sintering on grain size distribution.
• Supplier-Purchaser Agreements: Facilitates clear communication and compliance by offering quantifiable measures (E-Rating and L-Rating) that can be specified in procurement contracts.
• Performance Assurance: Assists in predicting material behavior under service conditions, contributing to the design and production of reliable, high-performance hardmetals.

Related Standards

ASTM B930-03(2021) references and complements other important standards in the field of powder metallurgy and hardmetals, including:

• ASTM B243: Terminology of Powder Metallurgy
• ASTM B406: Test Method for Transverse Rupture Strength of Cemented Carbides
• ASTM B657: Guide for Metallographic Identification of Microstructure in Cemented Carbides
• ASTM B665: Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides

By following the procedures in ASTM B930-03(2021), laboratories and manufacturers can reliably evaluate the grain structure of cemented tungsten carbides, promoting enhanced quality, performance, and consistency in hardmetal applications. This standard is recognized internationally and aligns with principles for standardization advocated by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B930 − 03 (Reapproved 2021)
Standard Test Method for
Rating Grain Size and Frequency of Abnormally Large
Grains in Cemented Tungsten Carbides (Hardmetals)
This standard is issued under the fixed designation B930; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.2 L-Rating—the size, in µm, of the largest grain ob-
served in a fully-etched specimen.
1.1 This test method describes a procedure for measuring
abnormally large grains and the frequency of those grains in
4. Summary of Test Method
cemented tungsten carbides (hardmetals).
4.1 Apolished and fully etched specimen/specimens having
1.2 This standard does not purport to address all of the
a minimum observable area of 0.5 cm is examined using a
safety concerns, if any, associated with its use. It is the
metallograph. Abnormally large grains, compared to the finer-
responsibility of the user of this standard to establish appro-
grained background material, are identified. These grains are
priate safety, health, and environmental practices and deter-
categorized as: ( 1) The number of grains larger than a
mine the applicability of regulatory limitations prior to use.
specified size, or ( 2) The largest grain observed, or both.
1.3 This international standard was developed in accor-
dance with internationally recognized principles on standard-
5. Significance and Use
ization established in the Decision on Principles for the
5.1 The microstructure and grain growth of cemented tung-
Development of International Standards, Guides and Recom-
sten carbides affect the material’s mechanical and physical
mendations issued by the World Trade Organization Technical
properties. The grain size and distribution will affect the
Barriers to Trade (TBT) Committee.
material’s wear resistance and fracture toughness.Abnormally
large grains as compared to the background may introduce an
2. Referenced Documents
area of weakness in a sintered part.
2.1 ASTM Standards:
5.2 This test method may be used in acceptance testing of
B243 Terminology of Powder Metallurgy
cemented tungsten carbide materials or the tungsten carbide
B406 Test Method for Transverse Rupture Strength of Ce-
powderusedintheirmanufacture.Thespecifiedgrainsizeused
mented Carbides
for the E-Rating is to be agreed upon between purchaser and
B657 GuideforMetallographicIdentificationofMicrostruc-
supplier.
ture in Cemented Carbides
B665 Guide for Metallographic Sample Preparation of Ce-
6. Apparatus
mented Tungsten Carbides
6.1 Metallographic Microscope, capable of magnifications
3. Terminology
of up to 1500×.
3.1 Definitions—Definitions of powder metallurgy terms
6.2 Ordinary metallurgical laboratory equipment.
can be found in Terminology B243.
6.3 Equipment for specimen preparation as outlined in
3.2 Definitions of Terms Specific to This Standard:
Guide B665.
3.2.1 E-Rating—the number/cm of grains larger than a
specified size in a fully-etched specimen. 7. Test Specimens
7.1 Specimen Size—The recommended specimen shall be
the standard transverse rupture specimen as specified in Test
This test method is under the jurisdiction of ASTM Committee B09 on Metal
Method B406; that is, ground to the following dimensions:
Powders and Metal Powder Products and is the direct responsibility of Subcom-
mittee B09.06 on Cemented Carbides.
5.00 6 0.25 mm (0.200 6 0.010 in) thick by 6.25 6 0.25 mm
Current edition approved Sept. 1, 202
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